When a Fisherman's Wharf shopkeeper shot and killed a pair of neighboring merchants three years ago, it was a calculated bid to right a perceived wrong and get rid of his competition in peddling knockoff purses to tourists, prosecutors said Tuesday.

But according to a defense attorney, Hong Ri Wu's attack in a tiny shop on Jefferson Street marked not a cold-blooded slaying but a breaking point for a man who had nearly lost his business.

As Wu's trial began with opening statements in San Francisco Superior Court, both prosecutors and Wu's attorney agreed that Wu, 59, killed Qiong Han Chu and Feng Ping Ou on Jan. 30, 2011. In fact, he repeatedly told witnesses and police officers that night that he gunned down the victims, who were both 30.

The question for the jury is in what manner Wu carried out the violence.

Assistant District Attorney John Rowland said the evidence will support two counts of murder. Deputy Public Defender Sandy Feinland asked the jury to find his client guilty of the lesser charge of manslaughter.

"These acts were not justified," Feinland said. "But this was not the cool, calculated decision the prosecution wants you to see it as. This was a rash act done in the heat of passion."

Wu had been struggling for some time to run his business selling knockoff purses at Fisherman's Wharf, and Chu and Ou had begun selling similar items in a larger storefront next door, authorities said.

Wu believed all of the merchants in the area had agreed - as part of their leases - not to sell the same products as other shopkeepers. He tried speaking to his landlord at least 10 times, his attorney said, but saw the landlord as biased in the dispute because she sold perfume out of the same storefront as Chu and Ou.

According to prosecutors, the last time Wu spoke to the landlord, he gave her a warning: "If I have to do something about it, I will have to resort to violence."

The landlord didn't take Wu seriously, Rowland said, and told him to take care of the problem himself. Eight days before the shooting, Wu brought a .45-caliber handgun registered in his name to his store and hid it under a pile of umbrellas, Rowland said.

Between 7 and 8 p.m. on the day of the killings, Wu loaded his gun with five bullets, put the weapon in a bag he had used to bring his lunch that day, closed the metal gate at his shop and went over to Chu and Ou's storefront, Rowland said.

He fired one round into Ou, who was at the front of the store, piercing her heart and lungs, Rowland said. Then he walked to the back, where Chu had ducked down and covered his head, and shot four more times at him.

"When he walked up to the young woman and pointed the gun at her, he said nothing - he didn't even know her name," Rowland said. "When he walked up to where the man was crouched, cowering in the back of the store, he said nothing."

Chu was an only son who took care of his elderly parents. Ou was a new mother and sole breadwinner for her family, with a 2-month-old daughter at home.

Wu was declared mentally incompetent to stand trial following his arraignment. He tried to commit suicide by refusing to eat, telling a sheriff's deputy in Cantonese, "I just want it to end."

Feinland said Wu had been bullied by the victims, who knew they were threatening his livelihood and weren't willing to negotiate. The defense attorney quoted the victims as saying, "We're not selling any of the same items. Really old man, you must be going crazy."

"We all have a breaking point," Feinland said.

Though Wu's trial began Tuesday, he was not in court for undisclosed reasons. The trial is expected to continue for at least two weeks.